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Phoenix Engineering speed control

I purchased the Phoenix Engineering speed control for my VPI Classic 3. I purchased  the bigger power supply and the tachometer combination of the speed control.  I notice that I can hear a steady hum coming from the speakers when the speed control us turned. The hum is constant and will not vary if I turn up the volume on the Preamp.  But the hum goes away when I turn the turntable off. The hum return when I turn on the turntable again. I even in unplugged the interconnect from the turntable, but it make no difference.  Does anyone with the Phoenix Engineering speed control experiencing the same issue?
almandog
sbank's avatar
sbank
2,038 posts
 
It's probably a ground loop. Do the table and/or the Phoenix have a ground wire? Try a cheater plug. Experiment with whatever ground wires there are between them and share the results with Phoenix when you call them. Cheers,
Spencer
buffyjames
38 posts
 
I agree with sbank....its a ground problem. If you use a cheater, only use it to confirm a ground issue...don’t keep it in the system....they ruin the sound. Use a voltmeter to see that all wall plugs are wired correctly. This can be very tricky to find.  I would get in touch with both Phoenix, and VPI and see if they have suggestions.  If I were in a betting mood, I would say that Harry has the answer.
sbank's avatar
sbank
2,038 posts
 
Harry usually does! 
almandog OP
117 posts
 
Yesterday i tried the Cheater plug and it worked. It was definitely the Phoenix Engineering power supply causing the hum.  I don't want to use a cheater plug in my system so I will move things around this weekend to see if I can get rid of that ground loop.
phoenixengr's avatar
phoenixengr
35 posts
 
sbank is correct, the hum is cause by a grounding issue.  The Eagle PSU uses a switch-mode power supply so the 3rd wire on the AC output is isolated from the wall socket ground.

If you are using a step up xfmr, ensure that the table's audio ground wire is connected to the phono pre-amp ground. Some SUTs can isolate this ground connection.

Try one (or both) of these:

Ground the case of the Eagle amplifier by attaching a ground wire to one of the rear panel screws;  connect the other end to a grounding point on your system.  Start at the phono pre-amp, main pre-amp, main amp or wall socket.  You may have to experiment to find the best location.

Isolate the 3rd wire ground on the table's power cord by using a 2 prong adapter; connect a ground wire to the adapter ground tab (3rd wire) and connect to your system's ground.


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